code: def MessageSetItemSizer(field_number):
      """Returns a sizer for extensions of MessageSet.
  
      The message set message looks like this:
        message MessageSet {
          repeated group Item = 1 {
            required int32 type_id = 2;
            required string message = 3;
          }
        }
      """
      static_size = (
          _TagSize(1) * 2
          + _TagSize(2)
          + _VarintSize(field_number)
          + _TagSize(3)
      )
      local_VarintSize = _VarintSize
  
      def FieldSize(value):
          l = value.ByteSize()
          return static_size + local_VarintSize(l) + l
  
      return FieldSize
  
imports: import struct
  import six
  from google.protobuf.internal import wire_format
label_desc: Use image node_id 11 for calling a global function with example usage: MessageSetItemSizer(field_number) and returns: FieldSize, unknown